Reciprocating duplex slurry pump



Dec. 8, 1970 K. SCHLECHT v RECIPROCATING DUPLEX SLURRY PUMP 6 Sheets-Sheet 1 Filed April 2. 1969 IL III In ventor= Dec. 8, 1970 K. SCHLECHT 3,545,893

RECIPROCATING DUPLEX SLURRY PUMP Filed April 2. 1969 6 Sheets-Sheet 2 Fi g. 2

X-i I a7 33 v 10 x K Inventor Kan sc /eagr 7" m /d wm Flee/v75 1970 K. SCHLECHT 3,545,893

RECIPROCATING DUPLEX SLURRY PUMP Filed April 2. 1969 s Sheets-Sheet 5 fi/l/TS Dec. 8, 1970 Filed April 2. 1969 K. SCHLECHT RECIPROCATING DUPLEX SLURRY PUMP I 6 Sheets-Sheet 4.

Inventor my I $c/ec1' IQ GENTS Dec. 8,1970 K. SCHLE CHT RECIPROCATING DUPLEX SLURRY PUMP 6 Sheets-Sheet 5 Filed April was Flam/7s 3,545,893 RECIPROCATING DUPLEX SLURRY PUMP Karl Schlecht, Bernhausen, Germany, assignor t Putzmeister G.rn.b.H., Chur, Switzerland Filed Apr. 2, 1969, Ser. No. 812,744 Claims priority, application Germany, Apr. 3, 1968, 1,703,112; Aug. 3, 1968, 1,703,946 Int. Cl. F04b 7/00, 17/00 US. Cl. 417-382 8 Claims ABSTRACT OF THE DISCLOSURE This invention relates to slurry pumps for mixed concrete and similar materials, and particularly to improvements in a known basic type of reciprocating duplex slurry pump.

The known pumps have long and narrow cylinders connected to a hydraulic system which pushes pistons in the cylinder in one direction while lengths of cable or like tension members pull the pistons back. The two lengths of tension members are connected in such a manner that one cylinder draws slurry from a container or the like while the other cylinder discharges a previously received amount of slurry under the pressure of the hydraulic fluid.

In some known pumps of this type, the two lengths of rope are integrally connected and move from one cylinder into the other through a packing which prevents leakage of hydraulic fluid from the cylinder under pressure to the simultaneously vented other cylinder. It is difiicult to maintain the required tight seal about the moving tension member, the friction in the packing causes relatively rapid deterioration of the tension member, and it is rather diflicult to replace a Worn-out tension member in such a pump.

Proposals made heretofore for improving the aforedescribed basic design led to a substantial increase in the bulk of the pump, or to very complex devices which were not fully satisfactory. A primary object of the invention is the provision of a slurry pump of the general type described above which is simple, compact, and relatively low in cost while capable of operating over extended periods without replacement of the ropes, cables, or other tension members.

It has been found that a pump satisfying the requirements set forth above can be obtained if the two tension members are wound on and unwound from drums mounted in the cylinders or in pressure chambers directly communicating with the cylinders proper for rotation about spaced parallel axes. A sprocket, gear, or other wheel member is fastened to each drum of the invention outside the cylinders for joint rotation with the drum about the axis of the same. The wheel members are connected by one or more motion transmitting elements in such a member that one of the tension members is wound on the associated drum while the other tension member is being unwound from the other drum.

Other features, additional objects, and many of the attendant advantages of this invention will readily become apparent fromthe following detailed description of a preferred embodiment when considered in connection with the appended drawing in which:

" United States Patent Office 3,545,893 Patented Dec. 8, 1970 FIG. 1 shows a pump of the invention in plan section on the axes of its cylinders and diagrammatically illustrates the associated hydraulic system partly in plan view and partly in elevation;

FIG. 2 shows one of the cylinders of the pump of FIG.

1 and some associated elements in elevational section on the line II-II in FIG. 3;

FIG. 3 shows the pump of FIG. 1 in plan view and partly in section on a scale larger than that of FIG. 1;

FIG. 4 shows the device of FIG. 2 in front-elevational section on the line IVIV and on a yet larger scale;

FIG. 5 illustrates the device of FIG. 4 in side-elevational section on the line V-V;

FIG. 6 shows one of the pistons of the pump of FIG. 1 and a portion of the associated cylinder in enlarged axial section;

FIG. 7 shows the apparatus of FIG. 6 in radial section on the line VIIVII;

FIG. 8 shows the housing in which the pressure chambers of the cylinder shown in FIG. 1 are received without its cover, the view being in rear elevation on a scale greater than that of FIG. 1; and

FIG. 9 shows a portion of the apparatus of FIG. 1 in top view;

FIG. 10 is a section along lines XX of FIG. 2.

Referring now to the drawing in details, and initially to FIG. 1, there is seen a duplex slurry pump of the invention with the associated hydraulic power and control circuits partly in plan view, and partly in elevation, a portion A of the apparatus shown in plan view being partly duplicated in elevation, and most of the apparatus being seen in section.

The pump has two identical cylinders 1, 2 whose parallel axes are much longer than the cylinder diameters and whose rear ends axially communicate with respective pressure chambers 3, 4. The front ends of the cylinders are connected by a valve housing 5.

Pistons 6, 7 are axially slidable in the cylinders 1, 2 respectively and are pulled backward alternatingly by associated tension members, such as cables or ropes 8, 9, one end of each tension members being wound on a drum 10 in the corresponding pressure chamber 3, 4. Trunnions 11 of each drum 10 are journaled in the top and bottom walls of the pressure chamber, as is better seen in FIG. 2, and one of the trunnions projects upward from the top wall of the chamber to carry a sprocket 12. A chain 14 is trained over the two sprockets 12 and a tension roller 13 which is spring loaded, as will be described in more detail with reference to FIG. 9.

Upright pins 15 of which only one is seen in FIGS. l-3, are attached to the chain 14 and engage a pivotally mounted sensing rod 16 fastened by a parallelogram linkage to a rocker 17 as the chain 14 moves back and forth. The rocker operates a distributor valve 18 in a hydraulic pilot circuit provided with oil under pressure by a pump 40 to operate double-acting, hydraulic valve actuators 19, 20 simultaneously, the lines connecting the pump 40 to the valve actuators 19, 20 being equipped with pressure limiting valves, gages, and manual control and shut-off valves, only partly illustrated and conventional in themselves so as not to require detailed description.

The valve actuator 19 operates a four-way valve 21 which controls the flow of water between a pump 41 driven by an electric motor 42, the two pressure chambers 3, 4, and a storage and expansion tank 43, a check valve 44 between the suction line 35 of the pump 41 normally permitting flow in a direction toward the tank 43 only, In the position of the valve 21 illustrated in FIG. 1, water is driven under pressure from the discharge line 34 of the pump 41 into the pressure chamber 4 while the chamber 3 is connected to the suction line 35. The valve 21 has been shown remote from the chambers 3, 4 in FIG. 1 for the sake of clarity, but it will presently be shown that it is actually attached to the chambers. The direction of flow to and from the cylinders 1, 2 will be reversed as soon as the piston 6 reaches its rearmost position when a pin will shift the sensing rod 16.

Simultaneously, a valves plate 22 is turned by the actuator in the valve housing 5 from the position seen in elevational section in FIG. 1. As is partly seen in more detail in FIGS. 2, 4, and 5, a storage and mixing vat 23 for concrete is mounted atop the valve housing 5. It is equipped with a paddle-type agitator 24 driven by a hydraulic motor 45 in circuit with an oil pump 46 and communicates directly with the valve housing 5. In the position illustrated in FIG. 1, the valve plate 22 directs the downwardly flowing concrete mixture into the cylinder 1, whereas the cylinder 2 is connected through a discharge elbow 27 with a non-illustrated pressure line.

The valve plate 22 is fixedly mounted on a shaft journaled in the housing 5 and carrying an operating arm 26 outside the housing. The arm is hingedly fastened to the valve actuator 20.

The piston 6 is shown in detail in FIGS. 6 and 7, and it will be understood that the piston 7 is identical with the piston 6. The backbone of the piston is a metal tube 61 coaxial with the cylinder 1. One end of the tube 61 carries a fixed radial flange 62. Four radial struts 63 on the other end carry a narrow guide ring 64. The narrow piston packing has a metallic core 65 which is a flat, rigid ring embedded in a ring 66 of elastomeric, relatively soft resilient material from which only the inner rim of the core 65 projects. The rim is held in abutting engagement with the outer edge portion of the fixed flange 62 by a circular disc or loose flange 67 attached to the fixed flange by bolts 68 and nuts 68, helical compression springs 68" being interposed between the flange 62 and the disc 67 to protect the soft ring 66. The circumferential portion of the ring 66 is axially enlarged to a length smaller than the internal radius of the cylinder 1 to form leading and trailing circular lips in sealing engagement with the inner wall of the cylinder 1.

A rod 69 is centrally attached to the disc or loose flange 67 and projects axially from the same. It cooperates with a fixed abutment on the cylinder 1 to limit the forward movement of the piston 6 if the tension member 8 should fail. The rear face of the plate 67 centrally carries two apertured lugs 70 which extend into the tube 61. A transverse pin 71 in the apertures of the lugs 70 passes through a thimble at the end of the cable 8 to fasten the piston 6 to the cable. A circumferential groove in the guide ring 64 accommodates a piston ring 72 of relatively soft plastic which slides along the cylinder wall with minimal friction during axial movement of the piston 6. The distance between the soft sealing ring 66 and the guide ring 72 is almost equal to the internal diameter of the cylinder 1.

As mentioned above, and shown more clearly in FIGS. 2 and 8, the four-way slide valve 21 which controls the flow of water toward and away from the pressure chambers 3, 4 is mounted on the rear face of the integrally connected pressure chambers inside and integrally incorporated in a pivotally attached cover 33 (FIGS. 2 and 10). As is seen in FIG. 8, this arrangement permits the suction and discharge lines 34, 35 to be fixedly attached to the partition 36 which separates the two chambers 3, 4. The connections between the lines and the cover 33 and the connections between the valve slide 21 and the two chambers 3, 4 are readily made watertight by means of packings made from round cord and placed in the cover 33 to prevent leakage from one line to the other, and from either line to the outside.

The cover 33 may be fastened by a non-illustrated hinge and a toggle closure. It gives ready access to the chambers 3, 4 for inspection and replacement of the tension members 8, 9, and for maintenance work on the valve 21. The valve 21 may be replaced as a unit together with the cover 33, if necessary.

FIG. 9 shows in more detail the tensioning of the chain 14. It is trained not only about the afore-described sprockets 12 and tension roller 13, but also engages a sensing roller 28. Two helical compression springs 29, 29', which abut against the stationary pump structure, urge the rollers 13, 28 against the chain 14. The roller 28 carries a movable contact 30. If the chain 14 is displaced by the pressure of the spring 29, the contact 30 engages first a fixed contact 31 and thereafter a fixed contact 32.

The chain is normally held tensioned by the water under pressure in the cylinders 1, 2. The chain tension drops only if the movements of the pistons 6, 7 are not properly synchronized or if the pressure drops in one of the chambers 3, 4 by loss of liquid from the water circuit or for other reasons. Synchronization may also be lost by a sudden increase in the back pressure of the concrete mixture in the elbow 27.

Deflection of the slack chain 14 under the pressure of the spring 29' causes a circuit to be closed first between the contacts 30, 31, and may trigger action to remedy the loss of tension, as by energizing a non-illustrated feed pump which drives additional Water from the tank 43 into the hydraulic circuit, or by simply energizing a bell and a light to attract the operators attention.

The contact 32 is part of an otherwise non-illustrated, conventional circuit of a relay in the controls of the motor 42. When the chain 14 becomes so slack that the contacts 30, 32 are engaged, the motor 42 is stopped, and no further concerete is discharged from the vat 23.

During normal operation of the apparatus, the piston 6 is drawn rearward by the cable 8 as the cable is being wound on the associated drum 10, the drum being driven by the chain 14 when the other drum 10 turns its sprocket 12 while the piston 7 is driven forward by water admitted to the pressure chamber 4 from the pump 41. The rearward movement of the piston 6 permits concrete mixture to flow from the vat 23 into the cylinder 1 through the valve housing 5 whereas the concrete mixture previously drawn into the cylinder 2 is pushed by the piston 7 through the valve housing into the elbow 27 and out of the pump. Water is returned from the chamber 3 to the suction line 35. When the piston 6 approaches its rearmost position, a pin 15 on the chain 14 engages the sensing rod 16 and reverses the pilot valve 18, whereby the direction of movement of the pistons 6, 7 is reversed, and the valve plate 22 is turned to direct fresh concrete mixture into the cylinder 2 and to empty the cylinder 1 into the elbow 27.

The reciprocating slurry pump of the invention occupies relatively little space. The chambers 3, 4 are low because the drums 10 turn in a common plane about radially spaced parallel axes. The chain transmission which connects them occupies no significant space, thereby permitting the relatively large water pump 41 and its drive motor 42 to be installed in the open central space between the cylinders 1, 2, the chambers 3, 4 and the valve housing 5, or directly beneath the common level of the principal pump chambers. A similarly compact arrangement is obtained if the chain transmission is replaced by gears on the trunnions 11, and by intermediate gears on a countershaft. A chain, or equivalent belt, however is preferred because of the simple manner in which such a flexible tension member may be employed for indicating trouble in the pump, as shown in FIG. 9.

Cams and cam followers have been used successfully instead of the pins 15 and the sensing rod 16 for sensing the positions of the pistons, and for reversing the power valve of the pump when the pistons reach a desired terminal position.

Devices commonly employed in hydraulic engineering and not required for normal operation of the slurry pump of the invention have not been described, and have partly been omitted from the drawing. It will thus be understood that the water circuits are equipped with safety valves which admit air to any portion of the circuit in which a pressure lower than atmospheric pressure should occur.

The slurry pump of the invention has been found to require replacement of the cables or other tension members '8, 9 at much longer intervals than otherwise comparable known pumps. The long life of the tension members is due in part to the absence of machine elements which frictionally engage the moving tension members and the minimal bending of the tension members during operation over the relatively large drums 10.

Another important feature of this invention is the reduction of sudden stress increases to which the tension 7 members of other pumps are subjected when the pistons reverse their directions of movement. Only the body of water behind the piston in one of the cylinders has to be stopped and reversed. The other cylinder is practically empty of water at this moment, and the valve 21 is so close to the cylinders that the amount of water in conduits between the intake and discharge lines 34, 35 and the cylinders 1, 2 is negligible. There is, of course, no reversal of flow in the lines 34, 35.

The specific configuration of the pistons 6, 7 as shown in FIGS. 6 and 7 materially contributes to the long life of the tension members 8, 9. The friction between the very narrow packing and guide rings 65, 72 and the cylinder wall is small, and is not significantly increased if sand particles or like constituents of the pumped concrete mixture should become embedded in the relatively soft rubber or similar material of the packing ring 66, and the plastic of the guide ring 72 which is somewhat harder, but still very much softer than metal. Yet, because of the wide spacing of the rings 66, 72, practically equally to the cylinder diameter, the piston is securely guided in the cylinder and cannot be tilted.

Any tendency of the piston to pivot in an axial plane is further reduced to a minimum by attaching the cable 8 to the flange 67 which is axially most remote from the guide ring 64 and its peripheral plastic insert 72.

FIG. 10 shows a vertical section of cover 33 parallel to the front side of the pressure chamber housing shown in FIG. 4.

Both narrow sides of cover 33 are provided with flangeconnected pressure cylinders 3-7, the pistons of which are formed by the two ends of rod 38 of four-way slide valve 21. To rod 38 are attached two valve disks 39 which alternately open and shut circular openings provided in four partitions of the slide valve arranged in parallel relationship. By means of these partitions and a transversely arranged circumferential wall designed to enclose these partitions the interior of the cover is divided into four chambers A, B, C and D. Chamber A is connected to return line 35 and centre chamber B is connected to feed line 34, whereas chambers C and D are connected to pressure chambers 3 and 4 respectively.

What is claimed is:

1. In a hydraulically operated slurry pump having two cylinders, a piston in each cylinder, a hydraulic system for admitting hydraulic fluid to a first axial end of each cylinder and for thereby driving the piston in said cylinder toward the second axial end of the same, and for venting the fluid from said first end, a tension member having one end attached to each piston for pulling the attached piston toward said first end, and motion transmitting means connecting the two tension members for releasing each tension member while the other tension member pulls the attached piston toward said first end, the improvement parallel axes, the other ends of said tension members being wound about the drum members respectively;

(b) a wheel member fastened to each drum member outside said cylinders for rotation with the drum member about said axis of the same; and

(c) motion transmitting means connecting said wheel members for Winding one of said tension members on the associated drum member while the other tension member is being unwound from the other drum member.

2. In a pump as set forth in claim 1, wherein said hydraulic system includes a source of hydraulic fluid under pressure, a power valve interposed between said source and said cylinders for admitting the fluid to one of said cylinders and for simultaneously venting the other cylinder, a fluid operated valve actuator connected to said valve for operating the same, and a pilot valve for operating said actuator, said improvement further comprising engageable means on said pilot valve and on said motion transmitting means for operating said pilot valve in response to movement of said motion transmitting means by one of said wheel members.

3. In a pump as set forth in claim 2, said first ends of said cylinders constituting respective pressure chambers, said power valve being mounted on said pressure chambers, and a cover pivotally secured to said pressure chambers and covering said power valve.

4. In a pump as set forth in claim 3, said hydraulic system further comprising a pump and two lines leading from said pump to said power valve, said chambers being separated by a partition fixedly fastened to said lines.

5. In a pump as set forth in claim 1, said motion transmitting means including a tension member trained over said two wheel members, tensioning means for normally tensioning said tension member in a predetermined path, a spring-loaded sensing member engaging said tension member and tending to deflect the same form said path thereof, and means for closing an electrical circuit in response to deflection of said tension member by said sensing member.

6. In a pump as set forth in claim 1, each of said pistons having an annular packing and a guide ring, said packing and said ring each engaging said cylinder over an axial length substantially smaller than the internal radius of said cylinder and being axially spaced from each other a distance not substantially smaller than the internal diameter of said cylinder, the portion of said cylinder axially intermediate said packing and said guide ring being radially spaced from said piston.

7. In a pump as set forth in claim 6, said packing inculding a rigid core portion and a resilient circumferential portion partly enveloping said core portion, the piston further comprising two flange members axially receiving said core member therebetween in clamping engagement.

8. In a pump as set forth in claim 7, a tubular member axially securing said guide. ring to one of said flange members, said one end of said tension member being received in said tubular member and secured to said one flange member.

References Cited UNITED STATES PATENTS 2,702,005 2/1955 Kruse l0344 2,802,424 8/1957 Lee 103-49 ROBERT M. WALKER, Primary Examiner US. Cl. X.R. 417-517 a 

